Double helical printer

ABSTRACT

A helical printing wheel having an alpha and numeric helical type element paths one being offset from the other by substantially one-half a character width to provide for the elimination of dead space on the wheel.

United States Patent 1 1 3,669,237 Wagner et al. [4 1 June 13, 1972 [54] DOUBLE HELICAL PRINTER [56] References Cited [72] Inventors: Robert L. Wagner, Menlo Park; Evan L. NTTE ATE PATENTS Raglan", Athemn both Calm 2,926,602 l/l960 MacDonald et 111.... 101/93 0 73 A A R it I C n S C l Robinson i sslgnee c31 1 n eg 8 orpora on, an at 08 3,526,309 9/1970 Marion et al.. ..l97/49 X 3,420,164 H1969 Lee ..l0l/93 C 22 Filed: May 4, 1970 Primary Examiner-Edgar S. Burr [21] Appl' 34437 Attorney-Flehr, Hohbach, Test, Albritton & Herbert 52 U.S. c1. ..197/49, 197/18, 101/93 c [57] ABSTRACT [51] Int. Cl. ..B41j 1/32 A helical printing wheel having an alpha and numeric helical [58] Field of Search 197/ 1 8, 55, 49; 101/93 C type element paths one being offset from the other by substantially one-half a character width to provide for the elimination of dead space on the wheel.

13 Claims, 12 Drawing Figures PATENTEDJuu 13 I972 SHEET l 0F 6,

0 M M a .5 w l 5. a 4 N Z L 6 F. N4 u I I P I 5 II m F -2 r 4 P P i 0 a u "a a mm W m :2 w 1 p 4 j i i l v i 3+ rui w M M m m m q qnawmx Max munufiuanzwwmm o m\ a O f. M p. M W L .t\\ a Z m I! Q w P! a m DOUBLE HELICAL PRINTER BACKGROUND OF THE INVENTION The present invention is directed to a printing device and particularly to a helical type of printer.

Helical printers normally consist of a print wheel having a helical path of characters thereon along with a juxtaposed hammer for bringing the print medium into contact with a type character. The greater the number of characters desired the larger are both the diameter and width of the print wheel. These increased dimensions are undesirable from many aspects. A larger diameter wheel necessitates a higher rotational speed to provide the same printing rate as a smaller diameter wheel. This reduces the amount of the time the hammer has to hit the character.

The foregoing is aggravated by increased width since the hammer force must correspond to the print wheel width. Thus, the mass of the hammer is increased reducing the speed at which the hammer may be actuated.

Another problem with helical printers is the need for dead space between the beginning and end of the character helix. Such space provides dead time to allow for the delay time in the actuating circuit of the hammer and its flight time. The dead space in effect requires a wheel of greater diameter and width with the attendant problems discussed above.

OBJECTS AND SUMMARY OF THE INVENTION It is, therefore, a general object of the present invention to provide an improved helical printer.

It is another object of the invention to provide a printer as above which has a print wheel with reduced diameter and width for a given number of characters.

In accordance with the above objects there is provided a printer comprising a rotatable device having type elements each having a predetermined and identical character position width for printing various characters on an object. The elements are located on the rotatable device in at least two separate helical paths the paths being offset from one another. Means are provided for rotating the device on its axis one revolution while traversing along its axis a character position width. Means are also provided for selectively bringing the type elements into contact with the object to be printed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a plan view of a printer embodying the present invention;

FIG. 2 is a cross-sectional view taken along the line 22 of FIG. 1;

FIG. 3 is a cross-sectional view taken along the line 3-3 of FIG. 1;

FIG. 4 is a cross-sectional view taken along the line 4--4 of FIG. 1;

FIG. 5 is an enlarged cross-sectional view taken along the line 55 of FIG. 1;

FIG. 6 is an enlarged view of a portion of FIG. 4 substantially taken along the line 66 with some structure omitted;

FIG. 7 is a pulse train useful in understanding the invention;

FIG. 8 is an example of the printing format of the present invention;

FIG. 9 is an enlarged folded-out representation of the printing wheel of the present invention which has been distorted in scale;

FIG. 10 is a plan view of a typical character on the printing wheel;

FIG. 11 is a block diagram illustrating the operation of the invention; and

FIG. I2 is a detailed block diagram of a portion of FIG. 11.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1, the printer of the present invention includes a rotatable printing wheel 11 having type elements for printing various characters on it which is mounted for rotation on a shaft 12 which is carried by a carriage 13. Carriage 13 is slidably mounted or journaled on rod 14 to allow wheel 11 to be moved transversely along its axis 12. Rod 14 is cantilevered from the side frame I6.

An eccentrically shaped rod 17 is mounted for rotation in frame 16 and also extends through carriage 13. The rotation of rod 17 around its center 17 moves carriage l3 and its associated printing wheel 11 up and away from a roller 18 which is permeated with printing ink which is mounted for rotation on frame 16. Eccentric rod 17 is rotated by means of a solenoid unit 19 mounted on frame 16 which is coupled to rod 17 by levers 21 and 22 (see FIG. 5). Carriage 13 also is slidable along eccentric rod 17.

.Iuxtaposed with printing wheel 11 is a hammer 23 with its associated actuator unit 24 which is slidably mounted on a rod 26 cantilevered from frame 16. As better illustrated in FIG. 2 the hammer actuator unit 24 also includes a U-shaped bottom segment 27 which moves along a cantilevered shaft 28.

The driving means for moving the hammer and its actuating unit in unison along with the wheel 11 and its carriage 13 are best shown in FIGS. 3 and 4 respectively. Specifically, in FIG. 3 a studded driving wheel 31 moves a perforated metal band 32 which is also passed around idler rollers 33 and 34 and is affixed to the actuator unit 24 for moving the hammer 23. This is also shown in FIG. 1 where the band 32 is affixed by screws 36 and 37.

Similarly, referring to FIG. 4, in the case of the carriage 13 for the printing wheel 11 a perforated band 38 is driven by studded drive wheel 39.

The overall mechanical driving system is best illustrated in conjunction with FIGS. 1 and 2. An electric motor 41 has an output drive shaft 42 which through belt 43 drives double pulley 44. This is coupled through a belt 46 to a drive pulley 47 of ink roller 18. Since roller 18 is normally in contact with printing wheel 11, its speed of rotation is therefore related to the rotary speed of the printing wheel 11.

Shaft 48 of double pulley 44 as best shown in FIG. 2 provides the drive for the transverse movement of hammer 23 and wheel 11 and also stores energy in a spring 59 for the carriage return movement of the elements 11 and 23. Shaft 48 has its speed reduced by a spur gear arrangement generally shown at 49 having an output on a shaft 51 which is coupled to a clutch 52. The output shaft of clutch 52 is coupled to studded wheels 31 and 39 to drive the actuator unit 24 and the carriage 13 of the wheel 11 in a direction, referring to FIG. 1, from right to left. During this movement spring 59 is loaded or wound. Upon reaching the left-most position the clutch 52 is released to allow for rapid return of both hammer and wheel to the start print position which is the right-hand position. For the carriage return movement suitable damping (not shown) is provided.

As also illustrated in FIG. 2 a suitable printing medium such as paper is provided by a paper roll 53 mounted on a shaft 54 which is cantilevered from frame 16. The upper 53 extends around guides 56 and 57 and then between hammer 23 and wheel 11. It is indexed by suitable line indexing means (not shown).

As illustrated in FIGS. 4 and 6 a code cup wheel 58 with peripheral notches or slots 59 is mounted for rotation with wheel 11. Arrow 61 shows the direction of rotation. One slot 59 which is deeper than the remaining slots is for the purpose of providing an index pulse and the remaining slots provide what is termed clock pulses. Mounted in the carriage unit 13 are photodetectors along with suitable juxtaposed light sources which in FIG. 6 are designed PCI and PC2. Photodetector PC2 is located axially inward in relation to the axis of the code cup 58 so that it is activated once per revolution. Photodetector PCI is positioned to be activated with the passage of every slot. This is illustrated in FIG. 7 where in the case where there are 44 characters 44 slots are provided. In accordance with the invention PC2 is located in a leading space phase relationship with PC I in a physical sense to provide an electrical phase lead of 180 as shown in FIG. 7. This provides for simplified logic circuitry.

FIG. 9 is a greatly expanded and somewhat distorted view of wheel 11 which indicates the character or symbol sequence and the associated circumferential sequence which have been given the decimal numbers 1 through 44. In addition, there is the reference level and the 90, 180 and 270 points are shown.

In accordance with the invention the type elements one of which is shown in enlarged form in FIG. 10 are arranged along 2 helical paths 62 and 63 one path being offset from the other. As best illustrated in FIG. 10 each character has a predetermined and identical character width 64 which in the preferred embodiment is 0.100 inches. The other dimensions of the particular character are also shown in FIG. 10. Wheel 11 has a side A and a side B and its directions of rotation and transverse movement are illustrated by the arrows 66.

The pitches of helical paths 62 and 63 are identical being equal to the character position width 64 divided by the total number of characters on the wheel which in this case is 44. Thus the pitch is in effect the distance indicated as 67 between the center lines of adjacent characters which is 0.100 divided by 44 or 0.0228 inches.

The velocity of traverse movement of wheel 11 is proportional to the pitch of the helical paths 62 and 63. For example, assume that it is desired to print 40 characters per second. Wheel 11 must therefore have a rotational speed of 40 revolutions per second. With a desired character width of 10.100 inches, 10 characters per inch must therefore be printed. Thus, the traverse velocity is equal to the quotient of the number of characters per second to be printed, which is 40, to the number of characters per inch which is 10, or four inches per second. Pitch is therefore related to the character width which is an integral factor in the speed oftraverse.

The characters of path 62 are of the alphabetical (alpha) type and of path 63 of the numeric type. This division is convenient from two aspects. First, the official ASCII code is divided into so-called alpha sticks and separate numeric sticks. In other words, a separate three digit binary code is used to differentiate alpha from numeric characters. Secondly, in the actual printing format, as especially used in the present invention, alpha and numeric characters are not normally intermixed.

Helical path 62 is offset from helical path 63 by the distance designated 68 which is the difference between the center line of the first character, A, of path 62 and the center line of the last character, 8, of the numeric helical path 63. In the present invention it has been found that this offset ideally is 0.041 inches. This offset distance 68 in the final analysis determines the spacing as illustrated in FIG. 8 between the printed alpha and numeric characters.

Referring now specifically to FIG. 8, the top line of alpha characters 69 illustrates the character position width which, since it is used to determine the pitch, determines both the total space of each character position and in addition the distance between the center lines of the characters, for example, F and G. Print line 71 which has all numeric characters shows their center line shifted from those of the alpha characters; however, the character position width of all characters is identical.

Print line 72 aptly illustrates the spacing caused by the helical path offset 68 of the printing wheel 11. In moving from right to left, which is the direction of printing, or from the 5 to M the space between the two characters position widths is equal to 0.041 inches or the actual offset distance 68. However, in moving from an alpha to numeric or from the M to the 5 the spacing is 0.059 which is the difference between the character position width and the actual offset 68. The reason for this is that because of the shift from the alpha to numeric an extra rotation of the wheel must be used to prevent overlapping the numeric with the alpha. In contrast, when proceeding from a numeric to an alpha character no extra wheel rotation or so-called skip of a revolution is necessary.

The offset 68 of 0.04l inches which is somewhat less than one-half the character position width has been chosen for esthetic reasons. In other words, it was decided when going from a numeric field to an alpha field to reduce that spacing somewhat and allow the alpha to numeric spacing to be larger. It is apparent that if exactly one-half a character width or 0.050 inches were used the spacing would be identical. In fact from a practical standpoint, the offset distance may be varied substantially 50 percent from one-half the character position width. This will allow good readability for the printout and yet prevent character overlap. The exact technique of skipping one revolution will be shown in conjunction with the discussion of FIGS. 1 1 and 12.

Referring now to FIG. 11, this block diagram shows the basic functioning of the printer of the present invention. A communications line indicated at 73 provides the printing of information in the standard ASCII code. A communications register 74 receives this information from the communications line and decodes any control code such as line feed (LF), carriage return (CR), start of message (SOM) and end of transmission (EOT) as best illustrated in block 75 to enable the printer to act on these commands as a message format. The remainder of the codes are transferred into a one line buffer unit 76. An encoder 77 converts the ASCII code into a straight binary code. This binary code is preloaded into the print register 78 in response to a printer load command 79 from encoder 77. Each binary code for a particular character corresponds to the decimal circumferential sequence on wheel 1 1. The encoder is set up for the particular printing wheel with which it is used. The printer load command occurs during an index pulse illustrated in FIG. 7.

In operation, the print register is preset to the binary number which coincides with the position of the character on the print wheel. This then is counted down to 0 by clock pulses (FIG. 7) from the space generator 81 and print control unit 82, produced by the slotted code cup of the printing wheel. When the countdown reaches zero, driver unit 83 is activated to fire the printing mechanism or the hammer indicated at 84.

The ready busy block 86 is a circuit to show the condition of the printer; specifically, whether or not it is ready to receive information or alternatively it is busy or in the act of printing or some other operation. The clock and character frame block 87 is a communications clock to provide the necessary format for receiving a code from the communications line and entering it into the one line buffer 76. One line buffer 76 is an MOS type 256 shift bit register. The oscillator and character frame unit 88 is both a clock and character framing circuit to determine whether there is any information in the buffer and if there is when the next character is to be operated on by the printer and how to locate it. Except for the space generator 81 which will now be discussed in FIG. 12, the blocks of FIG. 11 are essentially old in the art.

Space generator 81 as shown in greater detail in FIG. 12 is coupled to print control unit 82 which produces both index pulses and clock pulses on the lines so indicated to encoder 77 and to a counter 78' which is a substantial portion of the print register 78. The purpose of the space generator is twofold. First, it remembers the last character printed and determines whether or not the next character will be in a different helical path or field and if so whether there is a change in the alpha field to the numeric field or vice versa. Secondly, if there is a change from the alpha to the numeric field (see FIG. 8, from the M to the 5) the space generator will automatically generate a space or skip a print operation for one rotation of the printing wheel. This produces the type of space between the alpha and numeric as shown in FIG. 8.

More particularly, the above is accomplished by inhibiting the countdown operation of the counter 78' during a change from an alpha to numeric character. Such a change is sensed by the lack of an alpha indication on one of the two inputs 91, 92 to an OR gate 93. These inputs are designated alpha sticks and correspond to the two alpha sticks of the standard ASCII code. The output of OR gate 93 is coupled to a flip-flop 94 on encoder has not encoded a numeric character the condition line will be low because of a lack of output from the OR gate causing the Q output to go from high to low. This is sensed by a differentiator 95 which sets flip-flop 97 to activate inhibit countdown circuit 98 to prevent any countdown of counter 78' A subsequent index pulse resets flip-flop 97 to allow the counter 78 to be counted down in its typical manner to then print out that particular numeric character. A change to an alpha stick would, of course, switch the flip'flop 94 to a high on its 0 output line, but differentiator 96 is unresponsive to therefore produce no change in flip-flop 97.

One application of the present invention is printing sales tickets which usually have the name of the goods or the customers name, a dollar amount, and a credit card number. Thus, with the use of two helical paths having different types of characters, one being alpha and one being numeric, this arrangement of paths readily lends itself to this type of printing. It will also be apparent that where, for example, three categories of characters are needed that the printing wheel could be subdivided into three helical paths. This would, of course, require that the logic be modified to provide additional skips in the system.

Thus, in summary the present invention provides a printer which by means of its plurality of helical paths eliminates the normal dead space in the printing wheel and at the same time provides a wheel with smaller width and circumferential dimensions with a given number of characters to allow higher rotational speeds.

We claim:

1. A printer comprising a rotatable wheel having type elements each having a predetermined and identical character position width for printing various characters on an object said elements being located on said rotatable wheel in at least two separate helical paths, said paths being offset from one another by less than said character position width, means for rotating said device on its axis one revolution while traversing along its axis a character position width, and means for selectively bringing said type elements into contact with said object to be printed.

2. A printer as in claim I where said selective means includes hammer means mounted for transverse movement with said rotatable wheel and juxtaposed with said helical paths.

3. A printer as in claim 1 where said rotatable wheel has only two helical paths one path having characters of one type and the other path characters of another type.

4. A printer as in claim I said rotatable wheel has only two helical paths having identical pitches one being offset from the other by one-half of said character position width with a tolerance of :50 percent of one-half of said width.

5. A printer as in claim 1 where each of said helical paths has an identical pitch which is determined by said character position width and the total number of characters on said rotatable wheel.

6. A printer as in claim 5 where said rotatable wheel is traversed along its axis at a velocity proportional to the pitch of its helical paths.

7. A printer as in claim 1 where said characters are arranged in two helical paths one of said paths being offset substantially one-half character position width from the other helical path.

8. A printer as in claim 1 together with means for determining which of said characters is to be rinted and including means for skipping a print operation for one revolution of said rotatable wheel in response to said determining means indicating a change from a character in one helical path to a character in a predetermined other helical path.

9.'A printer as in claim 8 where said determining means includes a counter which is preloaded with a number corresponding to the character to be printed and said skipping means inhibits operation of said counter for one revolution of said rotatable wheel.

10. A printer as in claim 1 including an ink roller mounted on a fixed longitudinal axis extending the length of the range of axial transverse movement of said rotatable wheel together with means for rotating said roller at a predetermined speed and together with means for coupling the periphery of said ink roller with the periphery said rotatable wheel whereby said rotatable wheel is rotated by said ink roller.

11. A printer as in claim 10 together with means for engag' ing and disengaging said rotatable wheel from said ink roller during axial movement of said rotatable wheel in one direction.

12. A printer as in claim 11 in which said engaging/disengaging means includes eccentric means mounted for rotary movement and coupled to carriage means on which said rotatable device is mounted for rotation for lifting said carriage and said rotatable wheel off of said ink roller.

13. A printer as in claim 1 where said rotatable wheel includes a slotted code cup having a number of clocking slots each corresponding to a character, one of said clocking slots being cut deeper than the remainder to serve as an index slot and together with two photodetectors and a juxtaposed light source between which said slots move, one of said photodetectors being positioned to be activated only by passage of said index slot and the other photodetector being positioned to be actuated by passage of said clock slots said one photodetector being located with respect to the other photodetector to be activated in a leading phase relationship.

53 .UNI'IED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,669,237 Dated June 13, 1972 Inventor(S) Robert L. Wagner Evan L. Ragland III It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 56, delete "upper" and substitute therefor --paper-- Column 3, line 29,, delete "10.100" and substitute therefor "ulOO-F- Signedand sealed this 13th day of November 1973.

(SEAL) Attest:

EDWARD M.PLETCIIER,JR. RENE D. TDGTMEYIIR V Attesting Officer Acting Commissioner of Patents 

1. A printer comprising a rotatable wheel having type elements each having a predetermined and identical character position width for printing various characters on an object said elements being located on said rotatable wheel in at least two separate helical paths, said paths being offset from one another by less than said character position width, means for rotating said device on its axis one revolution while traversing along its axis a character position width, and means for selectively bringing said type elements into contact with said object to be printed.
 2. A printer as in claim 1 where said selective means includes hammer means mounted for transverse movement with said rotatable wheel and juxtaposed with said helical paths.
 3. A printer as in claim 1 where said rotatable wheel has only two helical paths one path having characters of One type and the other path characters of another type.
 4. A printer as in claim 1 said rotatable wheel has only two helical paths having identical pitches one being offset from the other by one-half of said character position width with a tolerance of + or - 50 percent of one-half of said width.
 5. A printer as in claim 1 where each of said helical paths has an identical pitch which is determined by said character position width and the total number of characters on said rotatable wheel.
 6. A printer as in claim 5 where said rotatable wheel is traversed along its axis at a velocity proportional to the pitch of its helical paths.
 7. A printer as in claim 1 where said characters are arranged in two helical paths one of said paths being offset substantially one-half character position width from the other helical path.
 8. A printer as in claim 1 together with means for determining which of said characters is to be printed and including means for skipping a print operation for one revolution of said rotatable wheel in response to said determining means indicating a change from a character in one helical path to a character in a predetermined other helical path.
 9. A printer as in claim 8 where said determining means includes a counter which is preloaded with a number corresponding to the character to be printed and said skipping means inhibits operation of said counter for one revolution of said rotatable wheel.
 10. A printer as in claim 1 including an ink roller mounted on a fixed longitudinal axis extending the length of the range of axial transverse movement of said rotatable wheel together with means for rotating said roller at a predetermined speed and together with means for coupling the periphery of said ink roller with the periphery said rotatable wheel whereby said rotatable wheel is rotated by said ink roller.
 11. A printer as in claim 10 together with means for engaging and disengaging said rotatable wheel from said ink roller during axial movement of said rotatable wheel in one direction.
 12. A printer as in claim 11 in which said engaging/disengaging means includes eccentric means mounted for rotary movement and coupled to carriage means on which said rotatable device is mounted for rotation for lifting said carriage and said rotatable wheel off of said ink roller.
 13. A printer as in claim 1 where said rotatable wheel includes a slotted code cup having a number of clocking slots each corresponding to a character, one of said clocking slots being cut deeper than the remainder to serve as an index slot and together with two photodetectors and a juxtaposed light source between which said slots move, one of said photodetectors being positioned to be activated only by passage of said index slot and the other photodetector being positioned to be actuated by passage of said clock slots said one photodetector being located with respect to the other photodetector to be activated in a leading phase relationship. 